Physiological deadspace in ventilated infants with differing lung pathologies

Abstract

Introduction: Physiological deadspace (V_DPHYS) comprises of the anatomical (V_DANA) and alveolar (V_DALV) compartments. Atelectasis in respiratory distress syndrome (RDS) and heterogeneous cystic parenchymal lung disease in evolving bronchopulmonary dysplasia (BPD) could contribute to changes in V_DPHYS.

Aims: To assess the physiological deadspace in infants with varying pulmonary conditions.

Methods: A prospective study of mechanically ventilated infants was undertaken. The modified Bohr-Enghoff equation was used to calculate V_DANA and V_DALV. Ethical approval was given by the London Research Ethics Committee.

Results: Sixty infants were included. Thirty-one infants with RDS, 15 infants with evolving BPD and 14 infants, ventilated for poor perinatal adaptation with no lung pathology, were controls. The infants had a median (IQR) gestational age of 29.2 (25.2-34.3) weeks and a birthweight of 1.1 (0.7-2.3) kg. Infants were studied at a median of 3 (2-8) days after birth. There were significant differences in V_DALV between controls (0.6 (0.3-1.3) mls/kg) and infants with either RDS (2.0 (0.9-3.6) mls/kg; p=0.001) or evolving BPD (2.5 (1.5-3.1) mls/kg; p=0.001). There was no significant difference in V_DALV between infants with RDS and evolving BPD (p=0.626), or in the V_DANA component between the different groups (p=0.125).

Conclusions: The higher alveolar deadspace in both the acute phase of RDS and that of evolving BPD may reflect underlying pulmonary abnormalities and disease induced changes. Assessment of V_DALV should be considered when determining appropriate volume targeting levels for optimal gas exchange in ventilated prematurely born infants.